1. Field of the Invention
The present invention relates to a radial-flow heat-dissipating fan. In particular, the present invention relates to a radial-flow heat-dissipating fan with increased inlet airflow.
2. Description of Related Art
FIG. 1 of the drawings illustrates a conventional radial-flow heat-dissipating fan comprising a casing 1, a cover 2, and a fan wheel 3. The casing 1 includes a compartment 11 and a side air outlet 12. The cover 2 is attached to the casing 1 and includes an air inlet 21. The fan wheel 3 is rotatably received in the compartment 11 and includes a hub 31, an annular plate 32, and a plurality of blades 33. In operation, the blades 33 are turned to draw axial airflow via the air inlet 21 of the cover 2. The airflow exits the side air outlet 12 of the casing 1 for dissipating heat from an object. The amount of inlet air is limited, as only one fan wheel 3 is used. The outlet air amount and the wind pressure are relatively low.
Taiwan Utility Model Publication No. 387512 discloses a radial-flow heat-dissipating fan comprising a primary fan wheel that includes a hub, an annular plate extending from the hub, and a plurality of blades on the annular plate. Further, a guiding fan wheel is securely mounted around a hub of the fan wheel and includes a plurality of blades close to the annular plate of the primary fan wheel. In operation, the guiding fan wheel turns together with the primary fan wheel, with the blades of the guiding fan wheel increasing air inlet amount, thereby increasing wind pressure and increasing air outlet amount. However, since the blades of the guiding fan wheel are almost in contact with the annular plate of the primary fan wheel and away from the air inlet, the inlet airflow is only increased by a relatively small amount via the air inlet. Further, since the direction of the axial inlet airflow could not be changed in time, the inlet airflow directly impinges the annular plate of the primary fan wheel, resulting in turbulent and noise. Further, since the blades of the guiding fan wheel are close to the blades of the primary fan wheel and thus block a portion of the blades of the primary fan wheel, the blowing efficiency of the blades of the primary fan wheel could not reach the expected result.